When the markets opened Thursday, Microsoft founder Bill Gates lost his standing as the world's richest man. That honor now belongs to Amazon founder Jeff Bezos. Amazon shares jumped Thursday morning, pulling up Bezos' net worth by $1.4 billion. As of 12 p.m. ET, Forbes' real-time list of the world's billionaires calculated Bezos has a net worth of $91.4 billion, while Gates' net worth now sits at a mere $90.1 billion. Aside from Gates and and Berkshire Hathaway CEO Warren Buffett, Bezos is the third American to make the list since its inception in 1987 and the seventh person to hold the top spot.